I'd like to enable that on existing cluster with bunch of pre-existing indexes but this proves to be difficult. Starting from scratch (same cluster version) is working but I'd rather have it enabled on main cluster.
You mentioned that x-pack changed in recent versions to overcome some of the issues above. Would you advise to try and upgrade version of the stack to the latest? I presume there was no major compatibility issues between 5.1.1 and current 5.5.1.
Thanks